I have a dear friend who has late stage Parkinson's Disease. At a local restaurant here, you go in and order and THEN you take a table. My friend cannot stand very long, so while her hubby was in ordering, she sat at a table. The waitress came by and said no saving tables. She NEVER tells people about her chronic condition until (and if) they become close friends. She explained that she needed to sit and that her husband was in line ordering. Too bad. You can't sit until he comes out. That made her mad, so she slowly walked up to the line (which by then was out the door with hungry tourists) to tell her husband she'd rather go elsewhere. While saying excuse me and trying carefully to get by ... she was pushed (almost knocking her over!) and told "no cutting in line."
She is drop dead gorgeous and looking at her, you would never think she is traveling the journey of painful chronic disease. She never complains. She is amazingly cheerful and how she can remain optimistic and thankful is beyond my comprehension.
So BEFORE you speak and prejudge someone's behavior ... physical or mental .... imagine that you don't have half the story. Maybe the person really is handicapped.